In the course of treating and preparing subterranean oil and gas wells for production, a well packer along with a production seal unit are run into the well on a work string, with the packer being set against a casing bore. During run-in, the packer is mechanically locked in the unset condition by shear pins. The shear pins support the weight of the packer along with the hang weight of other components such as a swivel shear sub, blank pipe, sand screen, polished nipple, tail screen, sealing unit and sump packer. The shear pins safely support the combined weight of the downhole equipment, and are rated to yield to a preset shearing force to separate and release the production seal unit after the packer has been set. The packer may be set in the sealing/anchoring configuration by application of hydraulic pressure applied through the work string. The packer may be released from the set configuration and retrieved from the well by appropriate manipulation of the tubing string and a specially designed releasing tool.
The purpose of a packer is to support production tubing and equipment such as a screen or safety valve adjacent to a producing formation and to seal the annulus between the outside of the production tubing and the inside of the well casing to prevent movement of fluids through the annulus past that location. The packer is provided with slip anchor members having opposed camming surfaces which cooperate with complementary opposed wedging surfaces, whereby the slip anchor members are extendable radially into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces. The packer also carries annular resilient seal elements which expand radially into sealing engagement against the bore of the well casing in response to axial compression forces. Longitudinal movement of the packer components which set the anchor slips and the sealing elements ma be effected either hydraulically or mechanically.